This invention relates to three-dimensional (3-D) acceleration detection and light modulation, and in specific to using two perpendicular laser beams focused on two ferrofluid cells to create two diffraction patterns whose deformations due to accelerations are used to visually display and detect the accelerations, and also using an electric or a magnetic field to modulate the intensity of light.
Laser produced interference fringes from mechanical type mediums have been previously detected in order to extrapolate movement detection. See for example, U.S. Pat. No. 3,354,311 to Vali et al.; U.S. Pat. No. 3,639,063 to Krogstad et al.; and U.S. Pat. No. 4,086,808 to Camac.
Laser produced interference fringe patterns have also been observed through ferrofluids by two of the co-inventors of the subject invention. See for example. Du et al. xe2x80x9cThermal Lens coupled magneto-optical Effect in a Ferrfluidxe2x80x9d, Applied Physics Letters 65(14). Oct. 3, 1994, pp 1844-1846; Du et al. xe2x80x9cDynamic Interference Patterns From Ferrofluidsxe2x80x9d, Modern Physics Letters 3, Vol. 9, No. 25(1995), pp.1643-1647; Zhang et al. xe2x80x9cTwo Mechanisms and a Scaling Relation for Dynamics in Ferrofluidsxe2x80x9d, Physical Review Letters Vol. 77, No. 2, July 1996, pp. 390-393: and Du et al. xe2x80x9cNonlinear Optical Effects in Ferrofluids Induced by Temperature and Concentration Cross-Couplingxe2x80x9d, Applied Phys. Letters 72(3), January 1998, pp 272-274.
Interference fringe rings have been created by passing laser beams through liquid crystals in order to measure the power density of the laser beam. See U.S. Pat. No. 5,621,525 to Vogeler et al., which is assigned to the University of Central Florida, the assignee of the subject invention.
However, the cited art are generally limited to detection of fringes along a single x and y axis. None of the cited prior art allows for the detection of fringe patterns along all three dimensions(x,y,z) to be useful as gyroscopes and accelerometers.
A first object of the invention is to provide a simplified, low-cost means of visually displaying accelerations using fringe patterns generated through ferrofluid samples.
A second object of the invention is to provide a method of modulating light intensity with two independent control fields.
The third objective of the invention is to provide a simple technique to display gravity visually through the diffraction patterns generated from the ferrofluids, which could be used by aerospace industries and NASA.
The fourth objective of the invention is to produce educational toys based on the principles discussed in this invention.
This invention relates to three-dimensional (3-D) acceleration detection and light modulation. In specific, the invention uses two perpendicular laser beams focused on two ferrofluid cells to create two diffraction patterns whose deformations due to accelerations are used to visually display and detect the accelerations. The invention also utilizes an electric or a magnetic field to modulate the intensity of light.
In the absence of accelerations, the subject invention demonstrates that a focused laser beam perpendicularly passing through a thin ferrofluid layer can generate concentric diffraction rings. The ferrofluid consists of magnetic particles suspended in kerosene. The strong light absorption of the particles causes nonuniform distributions in both temperature and particle concentration, yielding a spatial distribution in the index of refraction of the fluid around the beam and forming the observed rings. This diffraction pattern is visually observable by placing a viewing screen, which may simply comprise a piece of paper, a suitable distance away from the layer in the forward direction of the beam.
For a fluid with a nonuniform distribution in its mass density, an acceleration might cause a convective fluid flow within the fluid. If this fluid motion yields a measurable result, the result in turn can be used to determine the acceleration, providing a fluid-based accelerometer. The generated diffraction rings can be used to display the effect of an acceleration on the thin ferrofluid layer. The mass density of the fluid around the beam is nonuniform in the radial direction due to the inhomogeneous radial distributions in both temperature and concentration.
Accelerations perpendicular to the layer, do not cause convective motions within the fluid, and the concentric rings remain unchanged. However, an acceleration parallel to the layer causes a convective flow and deforms the rings. These deformed rings are easily visible to the eye, providing a qualitative and convenient means to visually display the acceleration. The measurement of the deformation in the rings can be used to determine the acceleration quantitatively, providing a method to measure accelerations when they are parallel to the layer. Since an acceleration can be decomposed into two accelerations perpendicular to each other and two perpendicularly placed ferrofluid cells can be used to display these two accelerations, an acceleration in any direction can be determined, providing a convenient 3-D ferrofluid accelerometer and gyroscope.
When an electric or a magnetic field is applied to a ferrofluid, the magnetic particles within the fluid have a strong interaction with the field, causing particles to move within the fluid. This interaction can be used to modulate the intensity of light passing through a ferrofluid sample.
Further objects and advantages of this invention will be apparent from the following detailed description of a presently preferred embodiment which is illustrated schematically in the accompanying drawings.